Semiconductor device and method of fabricating the same

ABSTRACT

Provided are a semiconductor device and a method of fabricating the same. The semiconductor device includes: an active region provided on a substrate; an inlet channel formed as a single cavity buried in one side of the substrate; an outlet channel formed as a single cavity buried in the other side of the substrate; a micro channel array comprising a plurality of micro channels, wherein the plurality of micro channels are formed as a plurality of cavities buried in the substrate, and one end of the micro channel array is connected to a side of the inlet channel and the other end of the micro channel array is connected to a side of the outlet channel; and a micro heat sink array separating the micro channels from one another.

CROSS-REFERENCE TO RELATED APPLICATIONS

This is a divisional application of U.S. patent application Ser. No.14/324,724, filed on Jul. 7, 2014, and allowed on Jan. 11, 2016.Further, this patent application also claims priority under 35 U.S.C.§119 of Korean Patent Application No. 10-2014-0002913, filed on Jan. 9,2014. The entire contents of these prior applications are herebyincorporated by reference.

BACKGROUND OF THE INVENTION

The present invention disclosed herein relates to a semiconductor deviceand a method of fabricating the same, and more particularly, to asemiconductor device having a cooling structure and a method offabricating the same.

As the capacity of home appliances and industrial systems increases andan electric vehicle (EV) and a hybrid/plug-in hybrid electric vehicle(HEV/PHEV) emerge, the usage of electrical energy sharply increases anda need for efficiently managing a electrical grid using a smart gridincreases. Thus, high power semiconductor devices as core componentsthat affect the efficient energy usage, stability, and reliability ofelectronic equipments become important recently. Also, as RF componentsand related systems in wireless communication and military service needbroad band frequency and high output power, the power density of RFsemiconductor devices also sharply increases.

These semiconductors are electronic devices used for converting orcontrolling electrical power or outputting a high-frequency RF signaland have a characteristic that they operate at a high voltage, a highcurrent, a high frequency, and high output power. For example, thesemiconductor devices may be transistors such as a metal oxidesemiconductor field effect transistor (MOSFET), a metal semiconductorfield effect transistor (MESFET), a high electron mobility transistor(HEMT), a junction field effect transistor (JFET), an insulated gatebipolar transistor (IGBT), and a bipolar junction transistor (BJT), aschottky or PiN diode, and a thyristor. When the semiconductor devicesare applied to modules, components and systems, the thermal managementof the devices is a core issue that affects the entire reliability. Thatis, when the thermal management is not properly performed, thesemiconductor device is locally heated in operation and a devicecharacteristic thus decreases or internal interconnections are degradeddue to the electromigration of atoms forming interconnections. As aresult, there is a limitation in that the semiconductor device wronglyoperates or is damaged. It is being reported that the fact also appearsin a CPU, an ASIC, a micro sensor, a micro actuator, a microelectromechanical system (MEMS), a high electrical power or high outputpower transistor and diode, accompanying occurrence of a hightemperature during operation. The cooling of a device comes to the forealso in a high output power laser diode (LD) and light-emitting diode(LED).

Typical cooling methods of electronic devices include attaching a thickmetal base plate and combining a heat sink emitting heat and thenperforming natural cooling or circulating a coolant with a fan or apump.

Recently, the device cooling is also performed by further fabricatingheat spreaders or a plurality of thermal vias on one or both sides ofthe semiconductor device. Also, there is an attempt to lower a devicetemperature by decreasing a thermal resistance using silicon carbide(SiC) or diamond, which is especially excellent in thermal conductivity,as a substrate.

Typical cooling methods have a complex form in which an external coolingdevice is assembled to the semiconductor device, and has a high thermalresistance because a volume and a thickness are especially large. Also,there is a limitation in that peripheral parts used for cooling are moreexpensive compared to the semiconductor device. In addition, there is alimitation in that there are needs for a complex semiconductorfabricating process or an expensive semiconductor substrate.

SUMMARY OF THE INVENTION

The present invention provides a structure that may be integrateddirectly into a semiconductor device, and a semiconductor device thatefficiently emits heat to easily cool a device and may be implemented bya semiconductor process.

Embodiments of the present invention provide semiconductor devicesincluding: an active region provided on a substrate; an inlet channelformed as a single cavity buried in one side of the substrate; an outletchannel formed as a single cavity buried in the other side of thesubstrate; a micro channel array comprising a plurality of microchannels, wherein the plurality of micro channels are formed as aplurality of cavities buried in the substrate, and one end of the microchannel array is connected to a side of the inlet channel and the otherend of the micro channel array is connected to a side of the outletchannel; and a micro heat sink array separating the micro channels.

In some embodiments, the substrate may include: a first surface on whichthe active region is arranged; and a second surface being the oppositesurface of the first surface, wherein the inlet channel, the outletchannel, the micro channel array, and the micro heat sink array may bearranged on the second surface of the substrate.

In other embodiments, an entry point on one end of the inlet channel andan exit point on one end of the outlet channel may be formed on sides ofthe substrate that face each other.

In still other embodiments, an entry point on one end of the inletchannel and an exit point on one end of the outlet channel may be formedon the same side of the substrate.

In even other embodiments, a cooling medium flowing through the inletchannel, the micro channel array and the outlet channel may include atleast one of liquid, gas, a mixture of liquid and gas, and supercriticalfluid.

In yet other embodiments, the micro heat sink array may include thesubstrate and a conductive layer.

In further embodiments, the single cavity forming the inlet channel, thesingle cavity forming the outlet channel, and the plurality of cavitiesforming the micro channel array may be connected to one another.

In still further embodiments, the substrate may include: a first surfaceon which the active region is arranged; and a second surface being theopposite surface of the first surface, wherein the conductive layer mayinclude: a first conductive layer provided on the second surface of thesubstrate; and a second conductive layer provided on the firstconductive layer, wherein the second conductive layer may seal thesingle cavity forming inlet channel, the single cavity forming theoutlet channel, and the plurality of cavities forming the micro channelarray.

In even further embodiments, the micro heat sink array may include aplurality of plates, wherein the plurality of plates may be distributedon the second surface of the substrate, extended in a first directionand spaced apart from one another in a second direction that crosses thefirst direction.

In yet further embodiments, the micro heat sink array may include aplurality of plates, wherein the plurality of plates may be distributedon the second surface of the substrate and spaced apart from one anotherin a first direction and in a second direction that crosses the firstdirection.

In much further embodiments, the micro heat sink array may include aplurality of cylinders, wherein the plurality of cylinders may bedistributed on the second surface of the substrate.

In still much further embodiments, the micro heat sink array may includea plurality of rectangular parallelepipeds, wherein the plurality ofrectangular parallelepipeds may be distributed on the second surface ofthe substrate.

In even much further embodiments, the conductive layer may include atleast one of an inorganic material, an organic material, and a mixedmaterial of the inorganic material and the organic material.

In yet much further embodiments, the conductive layer may be formed in asinge layer or in multiple layers.

In other embodiments of the present invention, methods of fabricating asemiconductor device include providing a substrate; forming an activeregion of a bottom of the substrate; forming a first conductive layer ona top of the substrate; patterning the substrate by etching using thefirst conductive layer as an etching mask to form a plurality of opencavities in the substrate; and forming a second conductive layer on thefirst conductive layer to seal the plurality of open cavities.

In some embodiments, the forming of the plurality of open cavities inthe substrate may include: anisotropically etching the substrateperpendicularly from the top of the substrate toward the bottom of thesubstrate by etching using the first conductive layer as an etching maskto form a plurality of trenches; and further isotropically etching theplurality of trenches to form the plurality of open cavities.

In other embodiments, the anisotropic etching of the plurality oftrenches may use reactive ion etching (RIE) or deep RIE.

In still other embodiments, the isotropic etching of the plurality oftrenches may use plasma etching or gas phase etching.

In even other embodiments, the forming of the first and the secondconductive layers may use e-beam evaporation or sputtering.

BRIEF DESCRIPTION OF THE DRAWINGS

The accompanying drawings are included to provide a furtherunderstanding of the present invention, and are incorporated in andconstitute a part of this specification. The drawings illustrateexemplary embodiments of the present invention and, together with thedescription, serve to explain principles of the present invention. Inthe drawings:

FIG. 1 is a plane view of a semiconductor device according to anembodiment of the present invention;

FIG. 2 is a cross-sectional view taken along broken line A1-A2 of FIG.1;

FIG. 3 is a plane view of a semiconductor device according to anotherembodiment of the present invention;

FIG. 4 is a plane view of a semiconductor device according to anotherembodiment of the present invention;

FIG. 5 is a plane view of a semiconductor device according to anotherembodiment of the present invention;

FIG. 6 is a plane view of a semiconductor device according to anotherembodiment of the present invention; and

FIGS. 7 to 12 are cross-sectional views of a method of fabricating asemiconductor device according to an embodiment of the presentinvention.

DETAILED DESCRIPTION OF PREFERRED EMBODIMENTS

A semiconductor device according to the present invention will bedescribed below in detail with reference to the accompanying drawings.

Advantages of the present invention over related art will become clearthrough the detailed description and the following claims along with theaccompanying drawings. In particular, the present invention is welldefined and clearly claimed in the claims. However, the presentinvention may be best understood by referring to the following detaileddescription in connection with the accompanying drawings. The samereference signs represent the same components in different drawings.

A semiconductor device according to embodiments of the present inventionis described below in detail with reference to the accompanyingdrawings.

FIG. 1 is a plane view of a semiconductor device according to a firstembodiment of the present invention. FIG. 2 is a cross-sectional viewtaken along broken line A1-A2 of FIG. 1.

Referring to FIGS. 1 to 2, a semiconductor device 1 according to anembodiment of the present invention may include a substrate 110, anactive region 120, an inlet channel 160, an outlet channel 180, a microchannel array 190, and a micro heat sink array 200.

The substrate 110 may include a cooling micro structure for cooling asemiconductor device 1. The substrate 110 may include silicon or othermaterials without limitation to the above-described material.

The active region 120 may be formed on the substrate 110 and function asan electronic device. The active region 120 may function as any one of atransistor, a diode, a CPU, an application specific integrated circuit(ASIC), a micro sensor, a micro actuator, and a micro electromechanicalsystem (MEMS).

The inlet channel 160, the outlet channel 180, the micro channel array190, and the micro heat sink array 200 may be buried in the substrate110. The inlet channel 160, the outlet channel 180, the micro channelarray 190, and the micro heat sink array 200 may be formed on theopposite side of the substrate that faces a side of the substrate 110adjoining the active region 120.

The inlet channel 160 is formed as a cavity buried in the substrate 110and an entry point 150 through a cooling medium 140 flows into thesubstrate may be formed on one end of the inlet channel. The inletchannel 160 may be connected to one end of the micro channel array 190.The inlet channel 160 may enable the cooling medium 140 to uniformlyflow from the outside of the substrate 110 to the micro channel array190 in the substrate 110.

The outlet channel 180 is formed as a cavity buried in the substrate 110and an exit point 170 that discharges the cooling medium 140 to theoutside of the substrate 110 may be on one end of the outlet channel.The outlet channel 180 may be connected to the other end of the microchannel array 190. The outlet channel 180 may enable the cooling medium140 to uniformly flow from the micro channel array 190 in the substrate110 to the outside of the substrate 110. The entry point 150 and theexit point 170 may be provided on sides facing each other (e.g., upperand lower sides or left and right sides) of the substrate 110.

The cooling medium 140 is a medium cooling the semiconductor device 1and may use a single phase material such as liquid or gas, a two-phasematerial formed by mixing gas and liquid, or supercritical fluid.

The micro channel array 190 may be formed as a plurality of cavitiesburied in the substrate 110. One end of the micro channel array 190 isconnected to the inlet channel 160 and the other end is connected to theoutlet channel 180 so that the cooling medium 140 may uniform flow inthe substrate 110. The micro channel array 190 may be a form in which aplurality of micro channels are connected to the inlet and outletchannels 160 and 180 for uniform flow of the cooling medium 140. How thecooling medium 140 flows may depend on the form of the micro heat sinkarray 200 that forms a plurality of barriers and separates microchannels from one another.

The cavity forming the inlet channel 160, the cavity forming the outletchannel 180, and the plurality of cavities forming the micro channelarray 190 may be connected to one another. The cavities may have aheight of about 20 μm to 200 μm.

As the aspect ratio W1/W2 of the micro heat sink array 200 increases,the surface region of the micro heat sink array 200 may increase. Thelarge surface region of the micro heat sink array 200 may easily inducetransfer of heat generated from the active region 120 to the microchannel region. The micro heat sink array 200 may include the substrate110, a first conductive layer 210, and a second conductive layer 220. Inorder to efficiently dissipate heat generated from the active region 120and lower a thermal resistance against heat transfer, the distancebetween the active region 120 and the micro heat sink array 200 may beshort.

The micro heat sink array 200 may function as a plurality of barriersthat divides the micro channel array 190 into a plurality of microchannels in the substrate 110. Cooling efficiency by the flow of thecooing medium 140 may be maximized by the micro heat sink array 200. Themicro heat sink array 200 may function as a supporting part thatsupports micro structures formed in the substrate 110. The micro heatsink array 200 may uniformly dissipate heat generated from the activeregion 120. The micro heat sink array 200 may have the shape of platesthat are arranged at a certain interval in a second direction D2 andextended in a first direction D1. The cooling medium 140 may flow intothe substrate 110 through the inlet channel 160 and may uniformly flowthrough the micro channel array 190. The heat generated from the activeregion 120 by the micro heat sink array 200 forming a plurality ofbarriers may be heat-transferred by a flow of the cooling medium and maybe discharged to the outside of the semiconductor device 1 through theoutlet channel 180.

The first and the second conductive layers 210 and 220 may be formed ofan electrically conductive material so that the entire substrate 110 mayfunction as a ground or electrode for the active region 120 whenpackaging the semiconductor device 1. The first and the secondconductive layers 210 and 220 may be formed of a material which has goodthermal conductivity. The first and the second conductive layers 210 and220 are formed in a single layer or in multiple layers and may include ametal such as Ti, Cr, Pt, Ni, Ag, Al, Ta, Mo, W, Cu, or Au, aninter-metallic compound or a metal compound such as TiW, TiN, TaN, WN,or NiV, or a nano material such as carbon nano tube (CNT) or graphene.The first conductive layer 210 may have a thickness of about 0.5 μm to 3μm and the second conductive layer 220 may have a thickness of about 20μm to 200 μm.

FIGS. 3 to 6 are plane views of semiconductor devices according to otherembodiments of the present invention; Differences between theabove-described embodiment and other embodiments are mainly describedbelow.

Referring to FIG. 3, a semiconductor device 2 according to anotherembodiment of the present invention may have the entry point 150 and theexit point 170 on the same side of the substrate 110. The micro heatsink array 200 may have the shape of plates that are arranged at acertain interval in a second direction D2 and extended in a firstdirection D1.

Referring to FIG. 4, a semiconductor device 3 according to anotherembodiment of the present invention may have the entry point 150 and theexit point 170 on sides of the substrate 110 that face each other. Themicro heat sink array 200 may have the shape of plates that are arrangedat a certain interval in a first and a second direction D1 and D2 andextended in a first direction D1.

Referring to FIG. 5, a semiconductor device 4 according to anotherembodiment of the present invention may have the entry point 150 and theexit point 170 on sides of the substrate 110 that face each other. Themicro heat sink array 200 may have the shape of rectangularparallelepipeds that are arranged at a certain interval in a first and asecond direction D1 and D2.

Referring to FIG. 6, a semiconductor device 5 according to anotherembodiment of the present invention may have the entry point 150 and theexit point 170 on the same side of the substrate 110. The heat sinkarray 200 may have the shape of cylinders that are arranged at a certaininterval in a first and a second direction D1 and D2.

The directions of the entry point 150 and the exit point 170 and themicro heat sink array 200 are not limited to the above-describedparticular structures but applications and variations may beimplemented.

FIGS. 7 to 12 are cross-sectional views of a method of fabricating asemiconductor device according to an embodiment of the presentinvention. In order to easily describe a process of fabricating asemiconductor device, figures are shown so that a part having a coolingstructure looks upward.

Referring to FIG. 7, the active region 120 may be formed on the bottomof the substrate 110. The width of the active region 120 may be smallerthan or the same as that of the substrate 110. The active region 120 mayfunctions as any one of a transistor, a diode, a CPU, an ASIC, a microsensor, a micro actuator, and an MEMS.

Referring to FIG. 8, the first conductive layer 210 that is anelectrically conductive material may be formed on the top of thesubstrate 110. The first conductive layer 210 may use e-beamevaporation, sputtering or other deposition techniques. The firstconductive layer 210 may be a single layer or multiple layers.

Referring to FIG. 9, a photosensitive material may be applied andpatterned onto the first conductive layer 210 to form a photoresistlayer 230. It is possible to form a micro line width part 240 bypatterning the first conductive layer 210 by using dry etching using thephotoresist layer 230 as an etching mask. If first applying thephotoresist layer 230, forming an image reversal on the photoresistlayer 230, depositing the first conductive layer 210 and removing theimage reversal by wet etching, it is possible to form the micro linewidth part 240 that includes only the first conductive layer 210,although not shown.

Referring to FIG. 10, after removing the photoresist layer 230, it ispossible to form a plurality of trenches 250 by patterning the substrate110 by an etching process using the first conductive layer 210 as anetching mask The trenches 250 may be formed by using anisotropic dryetching in a direction perpendicular to the substrate 110. As theanisotropic dry etching, reactive ion etching (RIE) or deep RIE that maydeeply etch the substrate 110 may be adopted. The depth of the trenches250 may define the approximate depths of the inlet channel 160, theoutlet channel 180, the micro channel array 190, and the micro heat sinkarray 200 that are subsequently formed. When there is a great differencein the line width of the micro line width part 240, the etching depth ofthe substrate 110 may be significantly different by a micro loadingeffect in a dry etching process.

Referring to FIG. 11, by further etching the substrate 110 by anisotropic etching process using the first conductive layer 210 as anetching mask, it is possible to form a plurality of open cavities 130for the formation of the inlet channel 160, the outlet channel 180, themicro channel array 190, and the micro heat sink array 200. Theplurality of open cavities may be connected to one another. A part notetched in the isotropic etching process may function as a supportingpart that supports micro structures formed in the substrate 110.

Referring to FIG. 12, the second conductive layer 220 that is anelectrically conductive material may be formed on the substrate 110including the first conductive layer 210 by using e-beam evaporation,sputtering or other deposition techniques. The plurality of opencavities may be sealed while a plurality of sealing parts 260 are formedas the second conductive layer 220 becomes thick. The second conductivelayer 220 may be stacked on the plurality of open cavities thin due tothe opening. The plurality of cavities sealed with the second conductivelayer may form the inlet channel 160, the outlet channel 180, and themicro channel array 190. Also, the inlet channel 160, the outlet channel180, the micro channel array 190, and the micro heat sink array 200 maybe buried in the substrate 110.

As described above, according to a method of fabricating an embodimentof the present invention, it is possible to, at a time, form allelements configuring an integrated cooling structure for a semiconductordevice that has any shape, size and depth by a semiconductor fabricatingprocess using only one sheet of pattern mask. Thus, the presentinvention has a simpler structure than typical cooling components for asemiconductor device, may be integrally fabricated on the semiconductordevice and it is possible to simplify processes and reduce manufacturingcosts.

According to an example of the present invention, a cooling structuremay be integrated directly onto the semiconductor device, it is possibleto easily cool a device by efficiently dissipating heat generated fromthe active region of the semiconductor device with a small structure andthe present invention may be implemented by a semiconductor process.

The detailed description of the present invention is not intended tolimit the present invention to embodiments disclosed herein and may beused under other combinations, changes and environments withoutdeparting from the subject matter of the present invention. Thefollowing claims should be construed as including other embodiments.

What is claimed is:
 1. A method of fabricating a semiconductor device,the method comprising: providing a substrate; forming an active regionof a bottom of the substrate; forming a first conductive layer on a topof the substrate; patterning the substrate by etching using the firstconductive layer as an etching mask to form a plurality of open cavitiesin the substrate; and forming a second conductive layer on the firstconductive layer to seal the plurality of open cavities.
 2. The methodof claim 1, wherein the forming of the plurality of open cavities in thesubstrate comprises: anisotropically etching the substrateperpendicularly from the top of the substrate toward the bottom of thesubstrate by etching using the first conductive layer as an etching maskto form a plurality of trenches; and further isotropically etching theplurality of trenches to form the plurality of open cavities.
 3. Themethod of claim 2, wherein the anisotropic etching of the plurality oftrenches uses reactive ion etching (RIE) or deep RIE.
 4. The method ofclaim 2, wherein the isotropic etching of the plurality of trenches usesplasma etching or gas phase etching.
 5. The method of claim 1, whereinthe forming of the first and the second conductive layers uses e-beamevaporation or sputtering.